There are solutions, slurries, suspensions and similar materials of organic origin in several industrial sectors, which have colloidal or granular solid phases (dry substance content) capable of absorbing large amount of moisture. The plastic grains of such materials containing large amounts of water can be partially dewatered by a heating effect, or the colloidal component can be granulated by heat effect. Since the mentioned materials can cause environment pollution and may certain valuable components utilizable for instance for animal feeding, industrial or agricultural purposes, the efforts of experts have been aimed at the extraction of valuable substances, and at the elimination of environment-damaging properties.
In slaughterhouses for instance large amount of waste materials, waste waters of high protein--and fat content are produced. Treatment of wastes and waste waters derived from slaughtering, splitting and gut cleaning plants causes many problems because the water consumption is very high in these plant units. Thus the waste waters contain the organic impurities in a highly diluted, often partially or completely dissolved state. Also the organic dry substance content of the canning industrial waste water is very high. In the organotherapeutic drug production, the valuable active ingredient is produced from animal organs, and treatment of organ fragments free from active ingredients derived in the course of production cause serious problems. The same applies to the waste material--occasionally of very high nutritive value--derived from agricultural and pharmaceutical frementation processes. The sludges of both communal and animal husbandry waste waters contain valuable materials which can be utilized, if extracted in a suitable form. However, so far no solution has been found for the economical extraction of the valuable material of suitable quality, e.g. protein, heparin, etc. from such wastes. Disadvantages of the presently known procedures are: multi-step, intermittent operation, no closed system exists, they are incapable of preventing the valuable materials of the wastes from decomposition and degradation. For instance processing of the raw materials collected for the purpose of meatmeal production begins in every case with the collection of the material. Thus decomposition and propagation of microorganisms begins even before the heat treatment. The intermittently treated material is stored periodically, and decay, decomposition and re-contamination set in. The heat treated material is to be dried, ground and finally its fat is extracted.
The fat extraction causes serious problems to the experts not only in the meatmeal production, but in other fields as well. The general characteristic of the solid grains present in the meat industrial waste waters (e.g. scraps of meat, intestinal villi, other undissolved by-products of high water content, e.g. large intestine with excrement, chitterlings, etc.) is the high fat content formed by the so-called surface and structural fats. Though part of the surface fat (fat tissues) can be removed before the meat processing with laborious manual work, these operations are not carried out in practice; the structural fat--representing the major part of the fat content--is not removable by preliminary cleaning. Although the voluminous offals are cut up roughly before processing, the fat cannot be removed in the course of cooking, heat treatment, then drying after the cutting. Consequently storable, non-sticky, non-rancid end product from meatmeal can be obtained only in grinding and partial fat extraction with organic solvents are carried out. This subsequent fat extraction entails not only significant cost (material, labor force, energy, investment), but an explosion hazard with solvents used in the plant. The method wherein cutting up the material enables the bulk of the fats to be melted with non-explosive medium, e.g. with hot water, then after removal of the melted fat and hot water the partially fat extracted fibres can be dried without after treatment, is not applicable rationally in practice. Separation of the solids of high water content and of very small grain size from the slurry (e.g. by filter press, filter drum, filter centrifuge) is not realizable, because the tiny grains clog the filter surface and a solid layer is formed. Separation of the fines from the slurry is then possible only with extremely costly screw separators and decanters requiring constant supervision. Decanter-type separation is used for instance for the separation of the protein fiber--derived at the so-called wet melting of lard carried out with 92-96.degree. C. steam--from the wet dissolved fat, and from extraction of plastic grains with high water content from the melted and heat treated blood.